Cloned mouse natural killer (NK) cells are highly cytotoxic for tumor target cells. The molecular mechanism of tumor cell lysis mediated by NK-cells will be investigated. Cytolysis effected by NK cells involves killer-target cell conjugation; intracellular transport of Golgi apparatus and NK-granules to the conjugation site; assembly and release of NK-cell generated vesicles into the interstitial space of conjugates; and the formation of large (160 Angstrom internal diameter) and small (approximately 50 Angstrom) membrane lesions detectable by electron microscopy. Membrane lesions are the result of the insertion into membranes of two types of tubular complexes, designated poly Perforin 1 (poly P1) and poly Perforin 2 (poly P2), that apparently form transmembrane channels on target membranes. Poly P1 and poly P2 appear to arise by polymerization of monomeric precursor perforins stored in NK-granules. Poly P1 and poly P2 in all probability represent the cytolytic effector units of NK-cells and may be the key to our understanding of cell mediated tumor cell lysis. The analysis of the formation of poly P1 and poly P2 by NK-cells and their transfer to target membranes is the subject of this research. The long range objective of this work is to isolate all components involved in the cytolytic mechanism and to define their specific function in molecular terms. For this purpose, poly P1 and poly P2 will be purified and specific antisera raised. The location of the precursor perforins will be determined. NK-cell granules will be isolated and their protein and lipid composition analyzed. Single bilayer vesicles released by NK-cells during the killing reaction will be isolated and their composition determined. In addition to using cloned mouse NK-cell studies with cloned human NK-cell lines will be conducted. And cytolytic cells not of NK lineage will be analyzed as to their content of perforins and their capability of assembling tubular complexes. It is expected that these studies will provide the basis for our understanding the molecular mechanism of cell mediated cytolysis and may enable us to intentionally manipulate cytolytic activity for the benefit of patients.